Method of and apparatus for cleaning tanks of vehicles



July 3, 1962v Filed Oct. 20, 1959 T. J. KEARNEY ETAL 3,042,553

METHOD oF AND APPARATUS Fon CLEANING TANKS oF VEHICLES 4 Sheets-Sheet 1dgame July 3, 1962 r. J. KEARNEY Erm. 3,042,553

METHOD OF' AND APPARATUS FOR CLEANING TANKS OF VEHICLES Filed Oct. 20,1959 4 Sheets-Sheet 2 A TTORNE YS.

July 3, 1962 T. J. KEARNEY ErAL 3,042,553

METHOD OF AND APPARATUS FOR CLEANING TANKS OF VEHICLES Filed Oct. 20,1959 4 Sheets-Sheet 3 su. "S S A TTORNE YS.

July 3, 1962 T. J. KEARNEY Erm. 3,042,553

METHOD OF AND APPARATUS FOR CLEANING TANKS OF' VEHICLES Filed Oct. 20,1959 4 Sheets-Sheet 4 INVENTORS. 0a S. mmasJZw/zf n A TTORNE YS.

United States Patent Ofice 3,042,553 Patented July 3, 1962 an g FiledOct. 20, 1959, Ser. No. 847,534

6 Claims. (Cl. 134-11) This invention relates to a method of and anapparatus for cleaning tanks or containers, such as are used in storing,transporting or processing ofuid commodities such as oils, grease, crudepetroleum products, petroleum asphalt, some coal tar products, resinousproducts, paints, and plasticizers and the like, with the ald of asuitable chlorinated solvent, for example: trichlorethylene,perchlorethylene or methylene chloride.

The effect of vapors of chlorinated solvents condensed on the interiorsof metal tanks to remove adhering oil, grease and the like, has beenlong known. However, the use of chlorinated solvents for this purposehas not been generally adopted because of its high cost and total lossof the solvent in the processing.

Our invention has for its chief aim to obviate the above mentioneddrawbacks. This objective is realized as hereinafter more fullydisclosed through provision of a simple method and a correspondinglysimple apparatus suitable for practice of such method by which tanks ofvehicle or the like can be effectively cleaned interiorly of dissolvableclinging matter with the aid of a chlorinated solvent in a minimum oftime and with negligible loss of the solvent.

As hereinafter more fully set forth, our improved tank cleaning methodis accomplished in three distinct successive steps or cycles, to wit:

(1) A cleaning cycle in which hot vapors of the solvent are continuouslycircuited through the tank for a predetermined time interval to dissolveand remove contaminated matter from the inner surface of the tank wall,in which the contaminated liquid incidentally formed is drained from thetank, and in which the solvent is extracted therefrom for re-use; (2) arecovery cycle in which air is circulated for a predetermined timeinterval through the tank to remove solvent vapors remaining aftercompletion of the scavenging cycle, and incident to which the solventvapors are condensed and this condensate is recovered; and (3) a finalor purging cycle in which outside air is drawn through the tank for apredetermined time interval.

Other objects and attendant advantages will appear from the followingdetailed description of the attached drawings, wherein:

FIG. l is a view in side elevation of a tank cleaning apparatusconveniently embodying our invention, and arranged for performing thescavenging cycle of the new method.

FIG. 2 shows the apparatus in top plan.

FIGS. 3 and 4 are views similar to FIG. 2, respectively showing theapparatus arranged for performing the recovery and purging cycles of themethod.

As herein exemplified, the apparatus comprises a solvent vaporgenerating unit 1 having a horizontally arranged cylindrical vessel 2which is kept filled with solvent approximately to the level indicatedat L in FIG. l. The solvent in the vessel 2 is continuously vaporized byheating means in the form of submerged steam coils 3 and 4, the steambeing conducted to said coils from a suitable supply source (notillustrated) by way of pipes 5 and 6 which are provided with owcontrolling hand valves 7 and 8. After traversing the coils 3 and 4 thespent steam is carried off through pipes 9 and 10 provided with handvalves 11, 12 and 13, 14 as well as with steam traps 15 and 16respectively. A bypass 17 with a valve 18 therein is shunted across theportion of the pipe 9 containing the valves 11, 12 and the steam trap15, and similarly, a bypass 19 with a valve 20 therein is shunted acrossthe portion of the pipe 10 containing the valves 13, 14 and the trap 16.Connecting into the top of the vessel 1 is a pipe 21 having a valve 22therein and whereto is connected a exible hose 23 that terminates in aspout tube 24 which is inserted downwardly through the filling opening25 of the tank 26 herein exemplified as being that of a highway truck27. At its upper end, the spout tube 24 is fixed in a cover plate 28temporarily substituted for the usual dome cover of the filling openingof the tank.

Also embodied in the generating unit 1 and arranged above the vessel 2is a condenser 30 having a coil 31 therein through which liquid coolant(which may be water) is passed, the inlet and outlet ends yof said coilbeing indicated at 32 and 33 respectively. Connected into one end of thehousing of the condenser 30 is a T-tting 35 to one end of which isattached a flexible hose 36, the distal end of said hose being connectedinto the cover plate 28 previously referred to. The other end of theT-fitting 35 is connected to the pipe 21 by a branch pipe 37 providedwith a hand valve 38. The condensate collecting in the bottom of thecondenser 30 is conducted, via a pipe 40, to a water separator indicatedat 41. Leading from the water separator 41 is a pipe 42 which meets witha pipe 43 connecting into the intake of a motor driven pump 45; andleading from the output of said pump is a riser pipe 46 which connectsinto the vessel 1 above the level L of the solvent as best seen inFIG. 1. Interposed in the pipe 42 respectively adjacent the separator 41and the pipe 43, are hand valves 47 and 48, and at a point between saidvalves is connected a solvent fill pipe 49. The riser pipe 46, on theother hand, is fitted with a check valve 50 and a flow indicating sightglass 51. Connected to the pipe 43, beyond a hand valve 52, is aflexible hose 53 whereof the distal end is removably coupled to a drainvalve 54 at the bottom of the vehicle tank 26. Leading from the end ofthe condenser 30 opposite that occupied by the T-fitting 35 is a pipe 55which joins an air intake pipe 56 provided with hand valve 57. Alsojoined to the pipe 5S is a branch pipe 58 which extends to the inlet ofa rotary motor driven blower 59 and which is fitted with a hand valve60. It is also to be noted that a pipe 61 extends from the lastmentioned end of the condenser 30 and connects into the top of the waterseparator 41 for the venting of said separator. Leading from the outletof the blower 59 is a pipe line 62, 69 having a valve 63 therein, andextending from the section 62 of said pipe line, and connecting into thepipe 21 beyond the valve 22 is a cross pipe 64 with a valve 65 therein.Also provided is a branch pipe 66 which extends from the pipe 55 andconnects into the pipe section 69 to the right of the valve 63, saidpipe 66 being likewise fitted with a valve 67. Surrounding the crosspipe 64 is a jacket 70 containing a heating coil 71 through which steammay be circulated for a purpose later on explained.

OPERATION Cleaning Cycle 4started to completely aerate the tank and 4,pass out through the pipe 21 and hose 23 and are discharged downwardlyfrom the lower end of the tube 24 into the bottom of the vehicle tank 26as shown by the arrows in FIG. 1. Due to the high density of the solventvapors as compared to that of the air, the vapors gather in the bottomof the tank. As the solvent vapors are continuously introduced, however,the air in the tank is displaced upwardly and forced out through thehose 36 into the housing of the condenser 30. By reason of having 4beenin contact with the solvent vapor some of the vapors are mixed with theair. As this gaseous mixture passes over the cold coils in the condenser3 0, its temperature is reduced with the result that practically all ofthe solvent vapors are condensed, and the now solvent-free air isexhausted from the housing of the condenser rby way of the piping 55,66, 68 and 69, and discharged into the outside atmosphere. As theoperation continues, the solvent vapors rise in the tank and some ofthem are condensed by the cold shell of the tank by radiation of theshell to the atmosphere, and thus wash off the oil, grease, crudepetroleum, petroleum asphalt or other adhering material (as the case maybe) and the contaminated condensate drains to the bottom of the tank,the excess vapors being all the while conducted through the conduit 36to the housing of the condenser 30. As the contaminated condensateaccumulates in the bottom of the tank 26, it is conducted through theflexible hose 53 to the pump 45 and by the latter forced through theriser pipe 46 into the top of the vessel 1, the cleaning cycle of theprocess being thus established.

Recovery Cycle After a lapse of a comparatively short time,approximately 25 minutes for a 5,000 gallon tank, for completion of thecleaning cycle, the supply of steam to the heating coils in the vesselll is cut olf by closing the valves 7 and 8, the valve 57 (air intake)valve 60 and valve 65 are opened, the valves 22, 63 and 67 are closed asin FIG. 3 and the blower 59 is started for the initiation of therecovery cycle. As a consequence, the solvent vapors and the solventladen air are withdrawn from the tank 26, and are conducted through thehose 36 into the housing of the condenser 30. In traversing thecondenser 30, the solvent content of the air is reduced to the quantityperature to which the air solvent mixture is cooled by the condensercoilf3l. This denuded air is then recirculated through the tank by wayof a piping 55, 58, blower 59, piping 62 and 64, valve 65 and exiblehose 23. As the solvent air mixture is cooled by the condenser coil 31,the solvent is condensed and this recovered solvent condensate drainsfrom the bottom of the condenser housing through pipe 40 into the waterseparator 41. From the separator 41 the solvent tlows through valve 47and pipe 42 into pipe 43 and is reintroduced into the vessel 2 of thevapor generator 1 by the pump 45. During the recovery cycle, the valve57 is left open so that air may enter to replace the volume of condensedsolvent vapors. The recovery cycle described above, that is the act ofwhich saturates the air at the low tem- 4" 57, 65 and 67 are closed andvalves 60 and 63 are opened and the hose 23 is uncoupled, as shown inFIG. 4. As a consequence, outside air can enter the downspout 24 toreplace the air discharged by the blower 59 through pipes 62 to 69, andvalve 63 to the atmosphere. The duration of this purging cycle will varyof course depending upon the ability to set the tank so that it willdrain perfectly.

Distillation of Used Solvent After a number of tanks have been cleanedin the above manner, by closing the valve 22 in the pipe 21 and openingthe valve 38, the vapors generated in the vessel 2 will pass through thepipe 37 into the condenser 30. The saturated solvent vapors thencondensed and co1- lected in the bottom of the condenser ow through thepipe 40 into the water separator 41, from which the recovered solventcan be piped to a suitable container (not illustrated) for collectionand re-use in the unit 1. The

vapor generating unit is thus a self-contained solvent still.

From time to time, the sludge collecting in the bottom of the vessel 2may be removed by opening the drain valve indicated at 72 provided forthat purpose.

While in accordance with the provisions of the statutes,

25 we have illustrated and described the best embodiment the appendedclaims, and that in of our invention now known to us, it will beapparent to those skilled in the an that changes may be made in the formof the apparatus described without departing from the spirit and scopeof the invention as set forth in some cases certain features of ourinvention may be used to advantage without a corresponding use of otherfeatures. Obviously, instead of being stationary, the apparatus of ourinvention may be mounted on wheels for mobility to different parts of aplant to clean tanks or receptacles, heat exreducing the solvent contentin the tank, results in reducing solvent losses to a very minimum. Theheater jacket 70 is intended to be used only when extremely lowtemperatures exist out-of-doors at the time the tank is being cleaned toheat the air prior to its introduction into the tank during the recoverycycle in order to more readily remove solvent from the cleaned tank byavoiding or minimizing possible excessive condensation of water vapor.

After a recirculating phase of ten to twenty minutes duration, dependingupon tank volume, all the solvent possible has 'been reclaimed and thepurging cycle is Purging Cycle In preparation for the purging cycle,valves 22, 38,

changers, fractionating columns, and other equipment such as is used inprocessing commodities of the kind hereinbefore referred to.

Having thus described our invention, we claim:

l. In a method of internally cleaning receptacles used in storing,transporting or processing commodities such as oils, grease, crudepetroleum products, petroleum asphalt and the like, the steps whichcomprise continuously boiling in a vapor generator a chlorinatedhydrocarbon solvent selected from the group consisting oftrichlorethylene, perchlorethylene and methylene chloride, continuouslyintroducing the hot vapors so generated into a receptacle to be cleanedand allowing said vapors to dissolve adhering matter from the innersurface of said receptacle, continuously conducting uncondensed vaporsand any air incidentally mixed therewith from the top of saidreceptacle, continuously cooling the gaseous mixture removed from thereceptacle to condense the solvent vapors therefrom and then exhaustingthe air to the atmosphere, removing entrained water from the solvent socondensed, then continuously returning the solvent so recovered to saidvapor generator for re-use in cleaning and finally passing unheatedoutside air through the tank to purge it of solvent odors and recoveringthe remaining traces of solvent vapor from the air before releasing theair to the atmosphere.

2. The method of claim 1 wherein the solvent contaminated with dissolvedmaterial removed from the walls of said receptacle and is continuouslyconducted to said vapor generator.

3. Apparatus for interiorly cleaning receptacles used in storing,transporting or processing commodities such as oils, grease, crudepetroleum products, petroleum asphalt and the like, comprising a vaporgenerator in the form of a vessel adapted to contain a chlorinatedhydrocarbon solvent selected from the group consisting oftrichlorethylene, perchlorethylene and methylene chloride, submergedheating means disposed in said vessel for boiling said solvent tovaporize it, a condenser with cooling means therein, an auxiliary coveradapted for application to the filling opening of said receptacle, saidcollecting in the bottom thereof cover having a spout tube extendingdownwardly therefrom to the bottom of said receptacle, conduit meansleading from said vessel above the solvent level therein and connectedby a llexible extension to said spout tube for conducting solvent vaporgenerated in said vessel to the bottom of said receptacle, furtherconduit means connected to said condenser and to said auxiliary coverfor conducting uncondensed solvent vapors from the top of saidreceptacle to said condenser, further conduit means connected to saidcondenser and to said vessel for conducting solvent back into saidvessel, a water separator connected with said conduit means between saidcondenser and said vessel for separating water from said solvent priorto the re-introduction thereof into said vessel, blower means connectedto said rst mentioned conduit means and operable after expiration of apredetermined period of time, for circulating air through saidreceptacle. and said condenser by way of said first and second mentionedconduit means to recover solvent from the vapors remaining in the tankand means for nally passing uuheated outside air through said receptaclefor a time to purge said receptacle of solvent odors, condensing anyremaining traces of solvent vapor from the air before exhausting the airinto the atmosphere, and incidentally recovering the condensate forre-use in the apparatus.

4. The apparatus dened in claim 3 wherein is ineluded further conduitmeans for conducting condensed solvent contaminated with matterdislodged from the walls of said receptacle and collected in the bottomthereof, from the receptacle to the generator.

5. The apparatus defined in claim 4 wherein a pump is interposed in saidthird-mentioned conduit means between said receptacle and said vessel.

6. The method of claim l with the additional step of admittingatmospheric air at a temperature below the boiling point of said solventinto said tank to circulate the solvent vapor in said tank to saidcondenser to condense said solvent vapors and substantially replace thesolvent vapor contents of said tank with atmospheric air.

References Cited in the file of this patent UNITED STATES PATENTS2,153,577 Levine Apr. 11, 1939 2,162,656 Warrington June 13, 19392,196,846 Andrus Apr. 9, 1940 FOREIGN PATENTS 11,561 France June l5,1839 470,419 Great Britain Aug. 16, 1937 UNITED STATES PATENT oFFICECERTIFICATE OF CORRECTION Patent No. 3,042,553 July 3, 1962 Thomas J.Kearney et al.

It is hereby certified that. error appears in the above numbered patentrequiring correction and that the said Letters Patent should read ascorrected below.

Column 1, line 30, for "vehicle" read vehicles line 38, for "circuited"Signed and sealed this 16th day of October 1962.`

SEAL) Attest:

:HNI-:ST w. swIDER DAVID L LADD

1. IN A METHOD OF INTERNALLY CLEANING RECEPTACLES USED IN STORING,TRANSPORTING OR PROCESSING COMMODITIES SUCH AS OILS, GREASE, CRUDEPETROLEUM PRODUCTS, PETROLEUM ASPHALT AND THE LIKE, THE STEPS WHICHCOMPRISE CONTINUOUSLY BOILING IN A VAPOR GENERATOR A CHLORINATEDHYDROCARBON SOLVENT SELECTED FROM THE GROUP CONSISTING OFTRICHLORETHYLENE, PERCHLORETHYLENE AND METHYLENE CHLORIDE, CONTINUOUSLYINTRODUCING THE HOT VAPORS SO GENERATED INTO A RECEPTACLE TO BE CLEANEDAND ALLOWING SAID VAPORS TO DISSOLVE ADHERING MATTER FROM THE INNERSURFACE OF SAID RECEPTACLE, CONTINUOUSLY CONDUCTING UNCONDENSED VAPORSAND ANY AIR INCIDENTALLY MIXED THEREWITH FROM THE TOP OF SAIDRECEPTACLE, CONTINOUSLY COOLING THE GASEOUS MIXTURE REMOVED FROM THERECEPTACLE TO CONDENSE THE SOLVENT VAPORS THEREFROM AND THEN EXHAUSTINGTHE AIR TO THE ATMOSPHERE, REMOVING ENTRAINED WATER FROM THE SOLVENT SOCONDENSED, THEN CONTINUOUSLY RETURNING THE SOLVENT SO RECOVERED TO SAIDVAPOR GENERATOR FOR RE-USE IN CLEANING AND FINALLY PASSING UNHEATEDOUTSIDE AIR THROUGH THE TANK IN PURGE IT OF SOLVENT ODORS AND REMOVINGTHE REMAINING TRACES OF SOLVENT VAPOR FROM THE AIR BEFORE RELEASING THEAIR TO THE ATMOSPHERE.